A CMP (chemical mechanical polishing) apparatus is used in a process of polishing a surface of a wafer in the manufacturing of a semiconductor device. The CMP apparatus is configured to hold and rotate the wafer with a polishing head, and press the wafer against a polishing pad on a rotating polishing table to polish the surface of the wafer. During polishing, a polishing liquid (or slurry) is supplied onto the polishing pad, so that the surface of the wafer is planarized by the chemical action of the polishing liquid and the mechanical action of abrasive grains contained in the polishing liquid.
A polishing rate of the wafer depends not only on a polishing load on the wafer pressed against the polishing pad, but also on a surface temperature of the polishing pad. This is because the chemical action of the polishing liquid on the wafer depends on the temperature. The polishing rate is an index indicating an amount (or a thickness) of a film of the wafer removed per unit time as a result of the polishing operation. The polishing rate is also referred to as removal rate.
Therefore, a CMP apparatus capable of regulating the surface temperature of the polishing pad has been developed. This type of CMP apparatus has a pad-temperature sensor and a pad-temperature regulation system. The pad-temperature sensor is arranged so as to measure the surface temperature of an area of the polishing pad that contacts the center of the wafer. The pad-temperature regulation system is configured to bring a heat exchanger into contact with the surface of the polishing pad to regulate the surface temperature of the polishing pad based on a measured value of the surface temperature of the polishing pad.
FIG. 12 is a diagram showing an example of a conventional heat exchanger. When a surface temperature of a polishing pad 200 is to be regulated such that a uniform temperature distribution is provided, a heat exchanger 201 is required to have a heating-fluid area 201A and a cooling-fluid area 201B inside thereof, as shown in FIG. 12. The heating-fluid area 201A constitutes a half of the inside of the heat exchanger 201, and the cooling-fluid area 201B constitutes the other half of the inside of the heat exchanger 201. With this configuration, as a polishing table 202 rotates, the heating-fluid area 201A and the cooling-fluid area 201B evenly contact the surface of the polishing pad 200, and as a result, a uniform temperature distribution is obtained. However, in order to shorten the polishing time, the surface temperature should quickly reach a desired target temperature. It takes time for the arrangement shown in FIG. 12 to reach the desired target temperature.
Thus, as shown in FIG. 13, there is a proposed heat exchanger 210 having a heating-fluid passage 208 and a cooling-fluid passage 209 which are arranged spirally. According to such an arrangement, it is possible to promptly reach a desired target temperature. However, in a peripheral portion of the heat exchanger 210, one of the heating-fluid passage 208 and the cooling-fluid passage 209 is dominant over another. As a result, the temperature distribution on the surface of the polishing pad 200 becomes nonuniform.